1. Field of the Invention
The present invention relates generally to a roll-up or curtain type modular security door system and, more particularly, to an improved adjustable tensioning arrangement for torsion springs utilized with modular, roll-up or curtain type security door systems.
This application relates to an improvement of U.S. Pat. No. 4,930,563, issued to Finch, et al., the disclosure of which is incorporated herein by reference as though set forth herein in haec verba.
2. Description of the Related Art
With ever-increasing urban crowding, the demand for storage space for infrequently used personal property has grown sharply. Such storage space, which used to be in a garage or basement, is not available in most apartments and condominiums, resulting in the development of the mini-warehouse or mini-storage facility. This type of facility features a secure, lockable storage space which is rented mainly to individuals. Since a wide variety of property may be stored in such facilities, including furniture and other large items, it is desirable to provide a large sealable door to provide access to individual storage areas. This eliminates conventional doors for the most part, since they are either too small or too unwieldy to be acceptable to the public.
Roll-up or curtain doors represent a convenient way to provide an easily operable closure, and they do so in a fairly limited space. Roll-up doors are typically constructed using a sheet of relatively thin metal which is formed by stamping or rolling to provide a plurality of horizontal corrugations extending the entire width of the door. This construction allows the door to be rolled up as it is raised for opening, thereby allowing the door to be stored in a cylindrical configuration at the top of the door opening., Vertical guide tracks, which may be made of extruded aluminum or formed galvanized steel, are typically mounted at opposite sides of the door opening and serve to guide the door as it moves up and down.
The top of the formed metal sheet is fastened to a barrel assembly which is constructed with a heavy wall, steel tube axle which supports thereon two or more galvanized steel drums or wheels. The barrel assembly is rotatably mounted between two brackets located slightly above the upper corners of the door opening. The barrel assembly is biased by one or two tempered steel torsion springs to balance the weight of the roll-up door, thereby allowing the door to be easily raised or lowered in a simple one-hand operation. Adhesively affixed tapes extend along the inner face of the door where contact is made with the galvanized steel drums or wheels to protect the door against wear by the galvanized steel drums or wheels, and to avoid rubbing of the successive layers of the roll-up door against each other.
The door also has a locking mechanism mounted thereon, which may be a simple sliding bolt type lock. With this mechanism, when the door is closed the bolt slides into a locking engagement with the guide track or with other metal means which prevents the door from being opened unless the bolt is opened. A simple padlock owned by the storage user may then be used to lock the bolt assembly.
This type of roll-up door is easy to operate, and will provide years of dependable service with virtually no maintenance. Such doors are relatively inexpensive, particularly when compared to similar roll-up doors which are made of a plurality of interlocking slats or panels.
Roll-up or curtain type doors represent a convenient way to provide an easily operable and secure closure. Spring arrangements, often involving torsion springs, are frequently used to ease the task of raising or lowering such doors.
In order to provide the desired reduction in force required to raise or lower a door, a spring arrangement must be properly tensioned. Frequently, this tensioning is performed during the construction or installation of the security door assembly. Because of this fact, the tensioning arrangement is fixed, and not easily adjustable to suit the particular needs of individual users. The degree of tensioning preferred by individual users varies over a wide range, and spring tensions set by a manufacturer during construction or unit assembly cannot accommodate this variability.
From the preceding description, it will be appreciated that such doors are relatively easy to manufacture, and the business of manufacturing them is quite competitive. Accordingly it is desirable to minimize the cost of manufacturing the doors as much as possible while still retaining a high degree of quality and reliability. The minimization of the number of different parts required is an objective which reduces the cost of manufacturing, and also reduces the number of different parts which must be stocked.
Minimizing the quantity of hardware components such as nuts and bolts is also desirable, from two standpoints. First, the cost factor mandates using the smallest number of hardware items necessary. Secondly, and even more importantly, since such doors are sold in complete kits, it is desirable to minimize the number of parts and by so doing the amount of assembly required. Owners of storage facilities must either install the doors themselves, or pay to have the doors installed. It is apparent that a door which is simple, easy, and quick to install will have a significant competitive advantage over doors that are not.
It will be appreciated that providing an easily adjustable tensioning arrangement for modular security door systems is desirable. Given that the business of manufacturing modular security door systems is quite competitive, it is also desirable to minimize the cost of manufacturing such an adjustable tensioning arrangement while still retaining a high degree of product quality and reliability. The minimization of the number of different parts required to be designed and fabricated serves to reduce the costs of manufacturing.
Accordingly, it is an objective of the present invention to develop a design minimizing the number of parts needed in fabricating a curtain type door, thereby reducing the cost and the amount of work necessary to install the door. To the greatest degree possible, the door should be of a modular design which further facilitates both kitting and installation. The door must be installable using only simple hand tools, and it must be simple to install. The tensioning arrangement must be capable of accommodating the tensions desired by individual users. Finally, the door must accomplish all of the aforesaid advantages while maintaining the highest degree of quality, durability, and dependability, and presenting no relative disadvantage.